Ibis最新文献

Monitoring vulnerable species inhabiting mountain environments is crucial to track population trends and prioritize conservation efforts. However, the challenging nature of these remote areas poses difficulties in implementing effective and consistent monitoring programmes. To address these challenges, we examined the potential of passive acoustic monitoring of a cryptic high mountain bird species, the Rock Ptarmigan Lagopus muta. For 5 months in each of two consecutive years, we deployed 38 autonomous recording units in 10 areas of the Swiss Alps where the species is monitored by a national count monitoring programme. Once the recordings were collected, we built a machine-learning algorithm to automate call recognition. We focused on studying the species' daily and seasonal calling phenology and relating these to meteorological and climatic data. Rock Ptarmigans were vocally active from March to July, with a peak of activity occurring between mid-March and late April, 1 or 2 months earlier than the second half of May when the counts of the monitoring programme take place. The calling rate peaked at dawn before dropping rapidly until sunrise. Daily vocal activity demonstrated a consistent association with weather conditions and moon phase, whereas the timing of seasonal vocal activity varied with temperature and snow conditions. We found that the peak of vocal activity occurred when the snowpack was still thick and snow cover was close to 100% but with a local peak of high temperatures. Between our two study years, the peak of vocal activity occurred 30 days later in the colder year, suggesting phenological plasticity in relation to environmental conditions. Passive acoustic monitoring has the potential to complement conventional acoustic counts of cryptic birds by highlighting periods of higher detectability of individuals, and to survey small populations that often remain undetected during single visits. Moreover, our study supports the idea that passive acoustic monitoring can provide valuable data over large spatial and temporal scales, allowing decryption of hidden ecological patterns and assisting in conservation efforts.

Bird migration is one of the greatest wildlife spectacles, producing massive global changes in the distributions of birds twice each year. To understand the evolution of this phenomenon, it is important to know the costs of these journeys in terms of the mortality they impose. The use of mark/re-sighting and tracking studies has now made it possible, for some bird species, to separate mortality during migration from mortality during stationary periods. This paper aims to assess this information, based mainly on 31 published studies, most of which concern long-distance migrations of passerines, large waterfowl and raptors. Most of these studies revealed that mortality rates were greater during migration than at other times – in some species more than 20 times greater. Overall, on the basis of median values, mortality per unit time during autumn journeys was about 3.0 times greater than mortality during stationary periods, during spring journeys about 6.3 times greater, and during autumn and spring journeys combined 4.4 times greater. The greater overall mortality on spring journeys was largely associated with more adverse wind conditions in spring than in autumn. High mortality rates were especially evident in birds crossing large ecological barriers, such as the Sahara Desert or the Gulf of Mexico, and were higher in that part of their journey than when crossing more benign terrain. There was no increase in mortality during migration in the adults of some long-lived species with high annual survival and predominantly overland journeys; for these birds, much larger samples of year-round tracked individuals will be needed to reveal any seasonal variations in mortality. Within certain species, birds that travelled long distances experienced greater mortality over the journey than those that travelled short distances, but in other species no such relationship was found. In species in which adults and juveniles were followed over the same journey, juveniles showed greater mortality. To judge from other studies, this difference could be attributed to the inexperience of juveniles, their lower feeding rates and flight efficiency, greater vulnerability to hazards such as weather and predation, or more frequent navigational errors. Broadly speaking, the risks of migration vary with features of the birds themselves, with the terrain to be crossed and with weather at the time. It may be assumed that migration persists in the long term because the costs (in terms of associated mortality) are more than offset by the benefits of breeding and wintering in different areas (in terms of improved overall survival and breeding success). To provide further understanding of migration mortality, suggestions are made on the types of studies required and on how they could best be conducted.

Leaving the nest early to avoid detection by an approaching predator is an often-cited form of nest defence among ground-nesting birds, yet has rarely been quantitatively demonstrated. During the breeding season, we recorded Flight-initiation Distances (FIDs) of incubating, off-duty and non-breeding Hooded Plovers Thinornis cucuallatus cucuallatus in Victoria, Australia. Hooded Plovers exhibited longer FIDs when incubating compared with when off-duty or non-breeding birds (the latter two categories had similar FIDs). Our study supports the Leave Early to Avoid Detection (LEAD) hypothesis, and demonstrates that so-called ‘passive’ defence is in fact an active decision by the incubator to leave nests at distances which exceed those at which birds without nests or off-duty commence escape.

Beginning in the mid-1990s, populations of three species of Gyps vultures declined by more than 97% in South Asia in little more than a decade, caused by unintentional poisoning by the non-steroidal anti-inflammatory drug (NSAID) diclofenac. This led to a ban on the veterinary use of the drug, and establishment of conservation breeding programmes, throughout the region. Once much of Nepal had been confirmed as being free from diclofenac, beginning in 2017 White-rumped Vultures Gyps bengalensis were released from the captive breeding population. A total of 99 birds (n = 50 wild and n = 49 released) were fitted with GPS transmitters between 2017 and 2022 and monitored daily. Tag fixes suggesting death or ill-health were followed up and dead vultures were retrieved for post-mortem analysis. The estimated annual survival of wild adult vultures was 0.974 (95% confidence interval [CI] 0.910–0.997), while that of wild subadults was 0.880 (95% CI 0.721–0.966). Survival rates of released birds were lower than those of wild birds, being 0.644 (95% CI 0.490–0.778) for adults and 0.758 (95% CI 0.579–0.887) for subadults. Post-mortem analysis of dead vultures indicated several possible causes of death, including predation, infection and electrocution. There was no evidence that any birds died of NSAID poisoning. The high survival rates of wild birds, especially adults, and the lack of evidence for NSAID-caused mortality, suggest that vulture habitat in the Nepal Vulture Safe Zone is free from diclofenac and that other hazards are sufficiently infrequent to allow the vulture population to recover. The lower survival of released birds compared with their wild counterparts suggests a need to improve the conservation breeding programme and release protocol.

A wide variety of attachment techniques have been used to track birds with electronic tags, with glue, tape, leg rings, neck collars and harnesses being the most common methods. In general, the choice of attachment method should strive to minimize tagging effects, but ensure that sufficient data are collected to address the research question at hand. The aim of our study was to develop and evaluate tag attachment methods to track Sandwich Terns Thalasseus sandvicensis during the last part of the incubation and the chick-rearing period of one breeding season. Tag attachments had to stay on for the duration of the chick-rearing period (5–6 weeks) and be non-restraining and flexible, but strong enough to withstand the forces and submersion associated with their plunge-diving foraging technique. We first experimentally tested the durability of flexible material under various environmental conditions with the aim of developing a self-releasing harness. Then, in field studies, we compared three different attachment methods on terns during the breeding seasons, attaching tags to dorsal feathers using (1) tape, (2) glue or (3) a newly developed harness made specifically for short-term deployments of one chick-rearing period and constructed from degradable material. Assessment of the performance of attachment methods was based on retention time of the loggers and on annual survival rates of tagged individuals in comparison with non-tagged individuals. The use of tape and glue led to premature loss of tags (median minimum retention time (range) of 3 (1–4) days and 15 (5–26) days, respectively), whereas the self-releasing harness had a median minimum retention time of 42 (18–91) days, which is sufficient to track Sandwich Terns during the entire chick-rearing period. The apparent annual survival of birds tagged using glue or tape did not differ from that observed in non-tagged control birds. In contrast, birds fitted with the self-releasing harnesses might have experienced a lower survival rate than control birds. Entanglement of birds in the harness material was incidentally observed in three cases, which may have contributed to the lower survival rates observed in this group. The risk of entanglement can potentially be mitigated with a leg-loop harness instead of a full-body harness. Our results highlight the necessity of careful consideration when selecting appropriate attachment methods. Specifically, there is a need to address whether the research questions and desired tracking duration justify the use of a harness and the higher impact that it entails, or whether a tape or glue-mount is sufficient. More broadly, sharing field expertise in tag attachments across studies is essential to successful deployments while minimizing the impact on animals.

The timing of migration varies significantly among individuals, even within populations sharing breeding sites. Consistent individual behavioural differences, known as personality traits, have been linked to variation in movement behaviour. However, little attention has been given to investigating whether personality traits can explain such variation in the timing of migration. We studied post-breeding migration of Red Knots Calidris canutus islandica breeding in the High Arctic and wintering in European coastal areas. We captured Red Knots in the Dutch Wadden Sea, a main non-breeding and moulting site, and assessed their exploration behaviour, a personality trait, before releasing them with colour-rings. We first investigated whether arrival timing in marine areas was associated with exploration speed. Secondly, we asked whether slow explorers were more likely to fly non-stop to the Wadden Sea compared with fast explorers, as faster explorers were expected to move more and visit more staging sites. To determine arrival timing in marine non-breeding areas and non-stop flights to the Wadden Sea, we analysed isotope signatures in blood samples collected after capture, as these differ between the terrestrial breeding grounds (arthropod diet) and marine non-breeding and moulting sites (benthic invertebrate diet). Thirdly, we estimated arrival time in the Wadden Sea based on primary moult progress, allowing us to examine the relationship between arrival timing estimated from isotope values and the onset of moult. Our findings revealed that slower exploring Red Knots departed earlier from the breeding site and were more likely to fly non-stop to the Wadden Sea than were faster exploring individuals. Arrival timing to marine areas as estimated from isotope analyses predicted arrival timing in the Wadden Sea (via moult progress) but this relationship exhibited significant variation, possibly due to individual differences in the use of staging sites en route. By migrating early, slower explorers can better outpace the aerial predators also arriving at the Wadden Sea moulting site and thereby reduce mortality risk due to predation.

The songbird trade crisis in East and South East Asia has been fuelled by high demand, driving many species to the brink of extinction. This demand, driven by the desire for songbirds as pets, for singing competitions and for prayer animal release has led to the overexploitation of numerous species and the introduction and spread of invasive alien species and diseases to novel environments. The ability to identify traded species efficiently and accurately is crucial for monitoring bird trade markets, protecting threatened species and enforcing wildlife laws. Citizen scientists can make major contributions to these conservation efforts but may be constrained by difficulties in distinguishing ‘look-alike’ bird species traded in markets. To address this challenge, we developed a novel deep learning-based Artificial Intelligence (AI) bioacoustic tool to enable citizen scientists to identify bird species traded in markets. To this end, we used three major avian vocalization databases to access bioacoustic data for 15 morphologically similar White-eye (Zosterops) species that are commonly traded in Asian wildlife markets. Specifically, we employed the Inception v3 pre-trained model to classify the 15 White-eye species and ambient sound (i.e. non-bird sound) using 448 bird recordings we obtained. We converted recordings into spectrogram (i.e. image form) and used eight image augmentation methods to enhance the performance of the AI neural network through training and validation. We found that recall, precision and F1 score increased as the amount of data augmentation increased, resulting in up to 91.6% overall accuracy and an F1 score of 88.8% for identifying focal species. Through the application of bioacoustics and deep learning, this approach would enable citizen scientists and law enforcement officials efficiently and accurately to identify prohibited trade in threatened species, making important contributions to conservation.

Breeding seabirds challenge the concept of niche segregation among competing species because similar competitors with comparable life histories can coexist in large multi-species colonies. This makes them an ideal model organism for studying the Hutchisonian niche model, which proposes interspecific niche segregation, across n-dimensions. Recent advances in assessment of ecological niches have improved our understanding of the mechanisms leading to at-sea segregation. We examine 152 published studies investigating one or more of three niche spaces in breeding seabirds: dietary items, stable isotopes (isotopic niche) and spatial distribution (horizontal and vertical). Most studies focused on one rather then multiple niche spaces in combination. When multiple niche spaces were combined, higher segregation than overlap was reported, compared with when niche spaces were assessed individually, as is predicted by the n-dimensional hypervolume concept. Studies investigating vertical (diving) foraging dimensions in addition to the more traditional horizontal (spatial) assessment reported more spatial segregation than overlap, compared with studies focusing only on horizontal or vertical dimensions. Segregation increased with colony size, suggesting an effect of competition. Segregation also increased during chick-rearing, when taxa were more phylogenetically distant, and when foraging ecology was more similar. To gain a comprehensive understanding of sympatric competitors' interactions and their ecological niche space, it is important to combine approaches and standardize methodologies. Embracing multidimensional approaches to assess niche segregation in seabird species can inform effective conservation and management practices in marine ecosystems.

Agricultural expansion and intensification drive changes in bird assemblages and contribute to the homogenization of communities. By working across the semi-arid biome of the Caatinga in northeastern Brazil, this study is the first to compare the bird communities found in intensively managed fruit farms with those in remnant Caatinga forest patches. We show that fruit farm patches host 56% lower bird abundance and 61% lower species richness compared with the remnant Caatinga forest fragments. Bird communities within the fruit farms were distinct from those within the forest patches, and they were characterized by species with broader niches, including two non-native species.

The Negros Fruit Dove Ptilinopus arcanus is an enigmatic bird known only from a single specimen collected on Negros Island, Philippines, in 1953. We extracted and sequenced ultra-conserved elements from historical toe-pad samples of the type specimen of P. arcanus and 27 other species of ptilinopine doves to investigate the species status and phylogenetic relationships of this taxon. We establish that P. arcanus represents a valid species, resolve its phylogenetic position at the base of the radiation of ‘core’ Ptilinopus fruit doves, and estimate that P. arcanus diverged from its most recent common ancestor several million years before Negros Island emerged from the seafloor. We also perform an ancestral range reconstruction to evaluate the effect of different altitudinal preferences on the putative historical range of this species, and we discuss how these findings can inform future efforts to relocate and potentially conserve this species.